交联聚乙烯/蒙脱土纳米复合物空间电荷特性研究

以十八烷基氯化铵处理的有机化蒙脱土(O-MMT)为无机纳米相,以低密度聚乙烯(LDPE)作为基体聚合物,以马来酸酐接枝聚乙烯(PEMA)为相容剂,以双叔丁基过氧化二异丙基苯BIPB为交联剂,通过熔融插层复合后再进行化学交联的"两步法",制备了交联聚乙烯/有机化蒙脱土(XLPE/O-MMT)纳米复合物.利用电声脉冲法(PEA)试验研究了不同蒙脱土含量的XLPE/O-MMT纳米复合物的空间电荷特性.实验结果表明,与纯XLPE相比,含一定比例O-MMT的XLPE/O-MMT纳米复合物具有不同程度抑制空间电荷的能力.当O-MMT含量为0.5%～1%时,其纳米复合物的空间电荷量最小;在O-MMT含量为3%～7%的范围内,随O-MMT含量的增加,XLPE/O-MMT纳米复合物中空间电荷量逐渐增大,但仍低于纯XLPE中的空间电荷量.通过热激电流(TSC)实验证实,与XLPE相比,XLPE/O-MMT纳米复合物的TSC峰均不同程度地向高温方向偏移,说明纳米复合材料的陷阱深度增加.当O-MMT含量为1 wt%时,TSC曲线所包围的面积最小,相应地,其陷阱密度最小;而随着O-MMT含量的增加,XLPE/O-MMT纳米复合物的TSC曲线所包围面积逐渐增大,说明其陷阱密度有所增加.绝缘电导率的试验结果进一步支持了上述观点.

STUDY ON SPACE CHARGE CHARACTERISTICS OF XLPE/O-MMT NANOCOMPOSITES

In the present paper cross-linked polyethylene/organic montmorillonite(XLPE/O-MMT) nanocomposites,in which organic montmorillonite(O-MMT) treated by octadecyl ammonium chloride as the inorganic nanophase,low density polyethylene(LDPE) as the matrix polymer,maleic anhydride grafted polyethylene(PEMA) as the compatibilizer and bis(1-(tert-butylperoxy)-1-methylethyl)-benzene(BIPB) as the crosslinking agent,are prepared by means of the two-step method,i.e.after melting intercalation process the cross-linking reaction is carried out chemically.The space charge properties of XLPE/O-MMT nanocomposites with different proportions of O-MMT are investigated by the pulsed electro-acoustic(PEA) method.The test results indicate that XLPE/O-MMT nanocomposites with certain content of O-MMT reveal the ability inhibiting space charge in different degrees compared with XLPE.In XLPE/O-MMT nanocomposites there is the lowest space charge amount when O-MMT content is 0.5 wt%~1 wt% and the space charge amount increases with O-MMT content in the range of 3 wt%~7 wt%,but it is still lower than that of XLPE.It is proved by the thermally stimulated current(TSC) tests that the TSC peak of XLPE/O-MMT nanocomposites shifts to higher temperatures compared with that of XLPE,and it is suggested that the traps depth increases.The area under TSC curve of XLPE/O-MMT nanocomposite with 1 wt% O-MMT is the least,accordingly its traps density is also the lowest;and the areas under TSC curves of XLPE/O-MMT nanocomposites increase with O-MMT content increasing,it means traps density enhancing.The test results of insulation electrical conductivity support the above conceptions further.